Optical Film Stack Safety Detection for Face Sensing Modules
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Solution Overview
Problem
Solid state lasers used in portable devices for face recognition and autofocusing cameras can pose safety issues if the diffractive optical element or glass is cracked or if there is a water drop on the light source, leading to potential eye damage due to concentrated laser energy.
Innovation Solution
An optical film stack with a diffractive optical element (DOE), a first detecting circuit layer, a liquid crystal changeable diffuser, and a conductive structure is used, where the liquid crystal diffuser includes transparent substrates and a liquid crystal layer, and the conductive structure connects detecting circuit layers to detect damage or water presence, enabling a safety detection function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a DOE and glass are used in the light source, then structured light can be formed for face recognition, but safety issues arise if the DOE or glass is cracked or if there is a water drop on or inside the light source
Solution Approach 1:
The patent combines multiple detecting circuit layers (first detecting circuit layer on DOE, second detecting circuit layer on first transparent substrate, third detecting circuit layer on second transparent substrate) into a unified safety detection system. These layers are integrated within the optical film stack structure and electrically connected through a conductive structure, allowing simultaneous monitoring of multiple components (DOE, transparent substrates) for cracks or water presence without requiring separate detection systems.
Solution Approach 2:
The detecting circuit layers serve multiple functions: they detect cracks in the DOE and transparent substrates, detect water drops on or inside the light source, and provide safety shutdown signals. The same conductive structure that electrically connects the detecting circuit layers also serves as part of the optical film stack architecture, achieving multi-functionality with integrated components.
2Reliability
If multiple detecting circuit layers are added to detect damage or water presence, then safety detection capability is improved, but device complexity increases
Solution Approach 1:
The patent implements a nested structure where the first detecting circuit layer is disposed on the DOE, the second detecting circuit layer is disposed on the first transparent substrate, and the third detecting circuit layer is disposed on the second transparent substrate. These detecting layers are nested within the optical film stack, with each layer integrated into its respective component structure. The conductive structure threads through these nested layers to electrically connect them, allowing comprehensive detection while maintaining a compact integrated design.
3Reliability
If the conductive structure connects all detecting circuit layers, then comprehensive safety monitoring is achieved, but manufacturing complexity increases
Solution Approach 1:
The conductive structure is designed to electrically connect the first, second, and third detecting circuit layers in advance during the assembly process. This preliminary electrical connection allows the safety detection system to be functional before final device assembly, enabling comprehensive safety monitoring coverage to be established early in the manufacturing process rather than requiring complex post-assembly wiring.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively detects breakage, damage, or water on the optical components, ensuring a safety detection function and preventing eye damage by ensuring the laser beam is safely directed.
Implementation Method 1
a liquid crystal layer (225) disposed between the first transparent substrate (222) and the second transparent substrate (224)
Data Source
Figure 1
Figure 2A~2C
Figure 3A~3B
AI summary
An optical film stack including a DOE, a first detecting circuit layer, a liquid crystal changeable diffuser, and a conductive structure is provided. The first detecting circuit layer is disposed on the DOE. The liquid crystal changeable diffuser is disposed beside the DOE and includes a first transparent substrate, a second detecting circuit layer, a second transparent substrate, a third detecting circuit layer, and a liquid crystal layer. The second detecting circuit layer is disposed on the first transparent substrate. The second transparent substrate is disposed beside the first transparent substrate. The third detecting circuit layer is disposed on the second transparent substrate. The liquid crystal layer is disposed between the first transparent substrate and the second transparent substrate. The conductive structure electrically connects the first detecting circuit layer, the second detecting circuit layer, and the third detecting circuit layer.